The present invention relates generally to firearms, and more particularly to firearms for firing grenades and other large projectiles. Some grenades are chemical, dispensing tear gas or nausea gas. Other grenades eject flares for signaling, marking rounds with smoke, phosphorous for lighting fires, and regular high explosive grenades for anti-personnel and anti-armor purposes.
The United States Army adopted the 40 mm M79 grenade launcher in the early 1960""s to provide the infantryman with an effective area-fire fragmentation weapon having a much greater range than possible with hand thrown grenades. Despite its effectiveness, the M79 is a single shot weapon limited to a low rate of fire. This low fire rate of single shot weapons can be a serious handicap because the grenadier is effectively disarmed while reloading the grenade launcher, providing the enemy an opportunity to attack or maneuver before the grenadier can further engage him. A further disadvantage with the M79 is that the rifle firepower of the infantry unit is reduced by one rifle.
Experienced grenadiers often do not use the weapon sights to establish a firing angle for the grenade launcher, but rather fire a first round at an angle of elevation based on experience. The grenadier observes the impact of this ranging round to make any required adjustment in the aim of the weapon at the target. Even though this technique is widely employed, it suffers from a disadvantage as employed with a single shot grenade launcher. The grenadier must lower the weapon to reload. Without exercising considerable skill, the weapon cannot be returned closely to its previous firing position to make the desired aiming correction, thus reducing the accuracy of the next fired round. Even if the grenadier can bring the target area under accurate fire, the delay between the ranging round and each succeeding round increases the time available for the target to take cover.
In order to address some of the problems associated with single shot weapons, the M203 grenade launcher attachment was developed for the M16 rifle. While the M16/M203 system provides the grenadier with rifle fire power in addition to grenade launching capabilities, the accuracy and grenade firing rate is degraded as compared to the M79 grenade launcher because of the increased weight and bulk of the combination weapon. In addition, the effectiveness of the M16 rifle attached to the grenade launcher is reduced.
Self powered weapon operating systems are commonly classified according to how energy is extracted from the propellant gases to operate the weapon. These systems can be classified as gas systems, recoil systems, and various types of blowback systems. These systems extract energy from the propellant gas and convert this gas into kinetic energy, which is imparted to the moving parts of the operating system. Weapon operating systems may also be classified according to the relationship of their primary and secondary masses. In gas, recoil and retarded blowback operating systems, most of the kinetic energy of the system is stored in a primary mass, typically called the bolt carrier or operating rod. The kinetic energy of the primary mass provides the energy for unlocking the secondary mass, which is typically called the bolt. After unlocking the secondary mass, the primary mass picks up the secondary mass and the two masses continue to recoil as a unit. Straight blow back weapons utilize only a primary mass.
Gas operated systems for grenade launchers are ineffective due to the internal ballistic characteristics of grenade cartridges. Grenade cartridges generate very low chamber pressure and a short pressure pulse. When coupled with the high expansion ratio of the cartridge, little gas pressure remains for operating the weapon.
Recoil operation of a shoulder fired grenade launcher presents difficulties because of the mount sensitivity of recoil operated systems especially since there is a low ratio of weapon mass to projectile mass in grenade launchers. Straight blowback operation for shoulder fired grenade launchers also presents difficulties because bolt recoil velocities cannot be kept within manageable limits without employing unacceptably massive bolts for a shoulder fired weapon.
There are also disadvantages associated with conventional retarded blowback operation of grenade launchers. The energy available for transfer to the operating mechanism in a retarded blowback operating system, as in a recoil system, depends on limiting receiver movement during firing, which is governed by the mounting resistance of the weapon. Grenade projectiles are relatively heavy when compared to the shoulder weapons in which they are fired; thus, grenade launchers are more sensitive to mounting resistance than are service rifles and machine guns. For example the M16 rifle weight to projectile weight ratio is about 800:1, and the M60 machinegun weight to projectile weight ratio is about 1000:1. In contrast, if a grenade launcher weighs 5 pounds, then the weapon to projectile weight ratio for a standard 40 mm grenade is about 13:1. This very low ratio associated with the grenade launcher is not conducive to reliable functioning in a conventional retarded blowback operating system. This is because the mounting resistance will vary greatly depending on whether the grenade launcher is held firmly against the shooter""s body or away from the shooter""s body, as well as the number of cartridges remaining in the magazine. If the receiver moves too far, then the receiver absorbs too much energy, thus reducing the energy available for driving the operating mechanism.
Multiple shot semi-automatic grenade launchers also have problems that relate to the recoil springs of the weapon. Conventional compression springs in weapon operating systems are limited to about 40 fps loading velocity; beyond which springs suffer from destructive spring surge. Therefore, the initial velocity of the bolt carrier must not exceed 40 fps.
A shoulder fired grenade launcher requires a relatively strong recoil spring to reliably chamber cartridges since the weapon is fired at high elevation angles and since the masses of a conventional bolt and of grenade cartridges are relatively large. This results in another problem associated with conventional box magazines relative to cartridge feeding and chambering grenade cartridges. A long overtravel for the bolt behind the top cartridge in the magazine is necessary to provide adequate time for the magazine follower spring to lift the cartridge stack to position another cartridge for chambering by the bolt. A relatively strong magazine follower spring must also be provided for adequate cartridge feeding. Additionally, a long chambering ramp is necessary which requires a long bolt travel, in spite of the next grenade cartridge typically being positioned as close as possible to the bore axis. Increasing the strength of the magazine follower spring causes the next cartridge in the magazine to exert a greater frictional or braking effect on the recoiling parts. Such compromises in the design of multiple shot grenade launchers using conventional magazines result in marginal reliability in cartridge feeding.
The relatively large mass of a grenade cartridge creates additional problems. An example of a multiple shot grenade launcher with a three chambered design is provided in U.S. Pat. No. 5,052,144. The grenade launcher of the ""144 patent includes a sliding horizontal magazine serving as a firing chamber that aligns each cartridge to be fired with the barrel. Since this magazine is displaced off-axis relative to the bore, the center of gravity of the magazine changes with each shot, causing the grenade launcher to recoil about a different center of gravity. The magazine described in the ""144 patent thus creates a different horizontal angle of departure for each shot relative to the line of sight, thus altering the point of impact of each projectile in azimuth.
While there have been attempts in the prior art to provide multiple shot grenade launchers, the need for improvements remains. Since the early 1960""s, continuing governmental and private industry attempts have failed to field any shoulder fired multiple shot semi-automatic grenade launchers. One reason for this failure is that grenade cartridges are very difficult to feed from the weapon magazine to the chamber. Grenade cartridges are large in diameter, short, blunt, fragile and heavy. Grenade cartridges with their fragile projectile ogives require special system design considerations in order to deliver the cartridge to the weapon chamber with the projectile undamaged.
The ogives of grenade service projectiles and various grenade training projectiles are fragile because of the thin windshields covering their fuses. Dye marker practice rounds, that have thin and brittle plastic ogives designed to break easily on impact, often break when dropped on a hard surface. Conventional feed systems designed for hard and tough projectiles are not designed to protect projectiles from damage during feeding and chambering. Neither do conventional systems isolate cartridges in the magazine or cartridges in the feed system from the jarring caused by the recoil of firing.
Large capacity grenade cartridge magazines used with experimental shoulder fired grenade launchers are usually of the detachable box or drum magazine types that are temporarily attached to the weapon. When empty, a detachable magazine is replaced with another loaded magazine. Placement of a large capacity magazine below the grenade launcher renders the weapon very awkward for firing from the prone position. Conventional box or drum magazines on grenade launchers are also awkward and uncomfortable when carrying on the march whether the magazines are in or out of the weapon.
Detachable grenade launcher magazines are notoriously bulky because of the geometry necessary to accommodate large cartridges in box and drum type magazines. In addition to the space required for the cartridges themselves, space is also required for the magazine follower and follower spring, as well as for the magazine body itself. Detachable magazines represent a substantial parasitic weight in the logistics system as well as in the ammunition burden of the soldier. Other types of grenade launcher magazine designs such as those using endless chains or belts are even more bulky for the number of cartridges carried. Such bulky magazines are very awkward for the soldier when aboard vehicles and for carrying into combat. Additionally, detachable magazines for grenade launchers are expensive.
The present invention is directed towards meeting some or all of the needs mentioned above while addressing some or all of the deficiencies discussed above.
The present invention is directed to, among other features, a weapon operating system that has application with grenade launchers and other devices for firing low pressure cartridges. The weapon operating system of one form of the present invention includes a breech lever and an accelerator lever, that transfer the recoil forces to the primary mass, such as an operating slide. The levers are disconnected from the primary mass as the primary mass recoils in the firearm. Thus the present invention does not require consideration of a secondary mass pick-up in the weapon operating system design. The design of the operating system mass requirement of the present invention may be based solely upon weapon cycling requirements since the ratio of the primary mass to secondary mass is not a design consideration. This permits a lighter weapon operating system.
In another form of the present invention, there is provided a weapon operating system that uses the energy provided from firing low pressure grenade cartridges. Low pressure grenade cartridges operate at very low chamber pressure with a short pressure pulse even though the recoil pulse is substantial. The recoil force from firing the chambered cartridge is transmitted to the weapon operating system. The weapon operating system includes a breech pad in communication with the cartridge. The breech pad is connected to a breech lever. The breech lever contacts an accelerator lever, and moves the accelerator lever when the cartridge is fired. The accelerator lever drives an operating slide provided with an extractor and a rammer. The extractor removes the spent cartridge from the chamber for ejection. The rammer picks up a second cartridge at the rear of the recoil stroke and positions the second cartridge in the chamber. Since the operating system does not require a bolt or bolt carrier, the mass of the recoiling parts is lowered significantly. Lower mass in the recoiling parts, in turn, increases the ratio of the mass of the weapon to the mass of the recoiling parts which inherently improves functional reliability.
In one form of the present invention, the breech lever is hinged off the barrel axis and perpendicular to the barrel axis. The accelerator lever is also hinged off the barrel axis opposite the breech lever hinge and perpendicular to the barrel axis. When the cartridge is fired, the breech lever and accelerator lever are each pivoted about their respective hinges and the breech lever and accelerator lever are swung away from the barrel axis and de-coupled from the operating slide during the recoil cycle.
According to another form of the present invention, there is provided a grenade launcher with a weapon operating system that addresses one or more concerns relating to the mounting resistance of the grenade launcher. In contrast to rifles and machineguns, grenade projectiles are relatively heavy when compared to grenade launcher weight. The operating system of the present invention transmits the recoil force from firing the cartridge through two levers and into a primary mass which is of relatively low mass as compared to overall weapon weight. In one specific embodiment, the empty weight of the weapon without the primary mass is about 4.25 lbs., and the primary mass weighs about 0.75 lbs. Since the primary mass is the only recoiling part of the weapon, the weight ratio of the weapon less recoiling parts to recoiling parts is about 5.66:1. This ratio is higher than would be found in a grenade launcher that has a secondary mass coupled to and recoiling along with the primary mass. The higher ratio of the present invention makes the grenade launcher less sensitive to changes in the mounting resistance provided by the shooter and the weight of cartridges in the magazine.
According to yet another feature of the present invention, there is provided a grenade launcher with springs between the receiver and the magazine housing that isolate the receiver and barrel from solid bearing against the magazine housing and the mounting resistance of the shooter. When the weapon is solidly mounted against the shoulder of the shooter and a cartridge is fired, the springs compress to permit the barrel and receiver group to recoil approximately as a free body relative to the magazine housing and the mounting resistance. If the grenade launcher is fired without mounting resistance, the entire weapon recoils as a free body. The grenade launcher is less sensitive to the mass of the cartridges remaining in the magazine and the mounting resistance provided by the shooter since the receiver and barrel are isolated from the magazine and mounting resistance. While isolating the magazine using these springs decreases the effective mass ratio of weapon plus projectile, the resultant mass ratio is effectively made more uniform between various mounting conditions.
According to another form of the present invention there is provided a magazine for retaining a column of grenade cartridges. Each cartridge of the column of cartridges has a nose and a tail, the tail defining a cartridge rim. The magazine has at least one interior surface defining a bore for retaining the column of cartridges. The interior surface extends along an axis between a front end and a rear end. The column of cartridges is stacked nose to tail substantially along the axis so that the nose of each cartridge points toward the front end. The magazine also has a magazine follower positioned at the rear end of the magazine for pushing the column of cartridges toward the front end. The magazine further includes a vernier member having a plurality of cartridge locators. The vernier member rides on a plurality of pins such that the vernier member is movable within the bore from a first position to a second position. In the first position the plurality of cartridge locators are disengaged from the column of cartridges. In the second position at least some of the cartridge locators engage the column of cartridges and displace the cartridges so engaged from contacting one another.
According to yet another form of the present invention there is provided a positive round control system for a grenade launcher. The positive round control system comprises a slide, cartridge carrier, carrier drive and drive pawl. The slide extends between a forward end and a back end. The slide has a recess substantially adjacent the rear end. The slide moves forward and back substantially along a bore axis of the grenade launcher. The cartridge carrier includes a lifter and at least one cartridge locator for securing a cartridge. The carrier drive is pivotally connected to the cartridge carrier by a carrier pin. The drive pawl is pivotally connected to the carrier drive and engages the recess of the slide during at least a portion of forward motion of the slide along the bore axis. The cartridge carrier is pivotally connected to a carrier link by a link pin so that the carrier drive and the cartridge carrier and the carrier link pivot around the link pin as a functional unit as the slide moves forward and the recess of the slide engages the drive pawl. The functional unit aligns the cartridge secured by the cartridge carrier on the bore axis of the grenade launcher. These and other features, aspects, embodiments, and advantages, including the cartridge feed mechanism and the cartridge magazine of the weapon, will be discussed further below.